This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Phototransduction is a signaling cascade whereby photon absorption is converted into a change in electrical current. Members of the phototransduction cascade are abundantly present in the thin outer segment compartment of the rod photoreceptor. Many of these proteins have been crystallized and high resolution structures have been deduced. However, it is not known how these proteins are assembled. The objective of this proposal is to obtain a detailed understanding of the signaling complexes in the vertebrate rod photoreceptor. The Chen laboratory has made a number of transgenic mice with targeted deletion of these proteins. Tomography of outer segments from these mice may be helpful in the reconstruction of the protein complexes involved in phototransduction.